linux-kernel - 2.6.34 rex64 sysret instruction setup not preserving flags (r11 contents and eflags do not match)

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Message-ID: <AANLkTikCrfH69IJ_SQRkziFQJj8N3hTTPPHUvLv4JorV@mail.gmail.com>
Date:	Fri, 2 Jul 2010 16:18:05 -0600
From:	Jeffrey Merkey <jeffmerkey@...il.com>
To:	linux-kernel@...r.kernel.org
Subject: 2.6.34 rex64 sysret instruction setup not preserving flags (r11 
	contents and eflags do not match)

On an AMD64 based system executing int 1 exceptions across a rex64
sysret, if the debugger sets the trap flag, r11 which holds the eflags
values for the
sysret return from syscall, the flags do not appear to get set
resutling in the int exception nesting by calling sysret over and over
again until the kernel stack
runs off the end.  Looks like the resume did not get set on this instruction.

sysret on AMD requires the flags be saved into r11 and what I am
seeing is the flags not matching what has been set in the pt_regs
struct.

Jeff
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